SUBSTANCE P-GENE-RELATED AND CALCITONIN-GENE-RELATED PEPTIDE-CONTAINING NERVE-FIBERS IN THE NASAL-MUCOSA OF CHRONICALLY HYPOXIC RATS

The distribution of substance P-immunoreactive and calcitonin gene-rel ated peptide-immunoreactive nerve fibers in the nasal mucosa was compa red between normoxic and chronically hypoxic rats (10% O-2 and 3.0-4.0 % CO2 for 3 months). In the normoxic nasal mucosa, substance P-and cal citonin gene-related peptide-immunoreactive nerve fibers were found wi thin and under the epithelium and around the glands and blood vessels in the lamina propria. These immunoreactive fibers have many varicosit ies. In the chronically hypoxic nasal mucosa, the relative density of intra-and subepithelial substance P-immunoreactive and calcitonin gene -related peptide-immunoreactive fibers and those in the lamina propria was higher than in normoxic mucosa. The length of substance P-positiv e fibers within the chronically hypoxic olfactory and respiratory epit helium was 1.66 and 2.45 times higher than within the normoxic epithel ium, respectively. The length of calcitonin gene-related peptide-immun ostained fibers within the chronically hypoxic olfactory and respirato ry epithelium was 1.56 and 1.84 times higher, respectively. Because su bstance P and calcitonin gene-related peptide are the predominant sign al peptides of primary sensory neurons, the increased number of these fibers may represent enhanced sensory mechanisms in the hypoxic nasal mucosa. In addition, considered together with the findings in chronica lly hypoxic tracheal mucosa, the increased density of intraepithelial fibers containing substance P and calcitonin gene-related peptide sugg ests that this is a predominant feature of hypoxic adaptation througho ut the upper and lower respiratory tracts. (C) 1998 Elsevier Science I nc.